In an effort to identify cell surface molecular sited mediating intercellular adhesions, lectins and antibodies that agglutinate the cells are being modified to produce non-agglutinating blocking agents specific for particular cell surface saccharide sites. The consequences of blocking such sites are determined through assays of cell aggregation and cell sorting. The native forms of non-agglutinating derivatives of lectins and antibodies that inhibit cell adhesion are then being immobilized on affinity columns and used to extract the corresponding cell surface glyco-substances from solution. These substances are then to be examined for their own effects on the adhesion of homologous and heterologous cells. In order to make possible the routine measurement of the intensities of intercellular adhesion within cell aggregates (aggregate sigma's), a new, rapid and relatively simple technique, the aggregate-oil drop fusion technique, has been conceived and partially developed. We propose to complete the development of this method and to apply it to test two important hypotheses: (1) that malignant invasive and metastatic behavior results from too-low intercellular adhesiveness, and (2) that certain morphogenetic tissue rearrangements result from particular kinds of intercellular adhesive differentials. A study of adhesion-guided pronephric duct morphogenesis will also be pursued until separate support for it is obtained. BIBLIOGRAPHIC REFERENCES: Poole, T.J. and M.S. Steinberg. 1977. SEM-aided analysis of morphogenetic movements: development of the amphibian pronephric duct. IITRI/Scanning Electron Microscopy, 1977, in press. Phillips, H.M., L.L. Wiseman and M.S. Steinberg. 1977. Self vs. nonself in tissue assembly. Correlated changes in recognition behavior and tissue cohesiveness. Devel. Biol. 57, in press.